This invention relates to voltage regulators such as a submicron CMOS voltage regulator circuit for providing a predetermined regulated voltage that is offset between first and second supply voltage rails.
Submicron CMOS circuits typically refers to CMOS circuits that include transistors having submicron gate lengths. In an effort to avoid reliability problems associated with high electric fields in the gate-drain region, CMOS circuits having submicron dimensions typically require a voltage supply not to exceed 3.3 volts instead of the typical 5 volts supply for CMOS circuits. The problem then arises of providing a reduced regulated power supply from an already existing 5 volt power supply.
One obvious solution to generating a reduced power supply is to insert diodes between each power supply rail thereby causing a voltage drop which reduces the power supply rail to rail voltage by the voltage dropped across each diode. However, it should be realized that the voltage drop across the diodes will vary with temperature and current, as is well known. This would have a negative effect of providing an unregulated power supply for a submicron CMOS circuit.
Hence, a need exists for a circuit providing a predetermined regulated voltage positioned between first and second supply voltage rails that is substantially independent of temperature and power supply variations.